1. Field of the Invention
The present invention relates to a document management system capable of managing a plurality of files as the files to be brought together into versions of one document, a method for controlling the document management system, and a program.
2. Description of the Related Art
In a document management system using a database, in a case where a file to be registered is managed in the database, storage disk amount used by the database increases with operation.
The basic function of a document management system includes a function to register a plurality of files generated at an editing process of a file time-sequentially as versions to manage the files as one document (a version management function). In the version management function, generally speaking, the file format of the file registered at the time of registering a document is determined and only the file format registered first can be used when the version of the document is updated thereafter. However, there exists a system different in a management system such as a document management system having a function to update a plurality of document formats as a version.
Japanese Patent Application Laid-Open No. 2003-263350 discusses management of a version for each page of a file. More specifically, the earliest version of a page is stored in a base page area, the page subjected to a writing operation is duplicated to a version page area to perform operation and, on the other hand, the page yet to be updated refers to the page in the base page area.
In general, a disk used for the database of the document management system is expensive, so that the operation cost increases according as the amount of use of a disk for storage increases.
Furthermore, in a case where data is transferred between document management systems different in a management system, such a problem is caused that the document of all versions cannot be registered in a database depending on the specifications of a document management system to which data is transferred.